O/B Re-engine

B

bayloon2

Cadet
Joined
Jun 1, 2011
Messages
6
Here's the situation:

I am completely refitting a near basket-case 30-year old Bayliner 2850 Contessa Sunbridge (27.5' LOA express cruiser) project boat for use exclusively on a small (less than 300 acres) protected lake. The factory engine, outdrive, fuel tank, windshield, and many other broken/non-functioning items have been eliminated reducing weight to around 5,000 lbs. My intent is to mount a single tiller O/B on the swim platform for leisurely, relatively quiet cruising around the lake on calm days. Ideally, I'd like to be able to get hull speed at idle out of a 9.9HP, but we all know that's a bridge too far. Barring an emergency, I don't intend to run at WOT, so I prefer to compromise speed for quiet. A couple MPH would be just fine at low throttle.

So with this thumbnail background, I'd sure appreciate your wisdom on what direction I should go. Thnx.
Wayne
 
G

Georgesalmon

Lieutenant Commander
Joined
Apr 14, 2012
Messages
1,793
Re: O/B Re-engine

Get a sailboat engine or a designed kicker. They have a different gear ratio that will turn a large 4 blade prop and give you the push you need. You can only get displacement speeds withot planing the hull. So you need a high torque motor. Good example would be a 9.9 merc pro-kicker, or Yamaha has an 8hp thats high torque to. 4 stroke is quieter.
 
R

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: O/B Re-engine

There's several electric outboards on the market(Torqueedo, others)that might be worth consideration....Totally Quiet...plenty for 300 acre lake! Install a battery charger and you're good to go!...QUIET!;)
 
H

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: O/B Re-engine

Galley slaves. And if you're good at it you can keep them right quiet.

Just that incessant drum beat takes some getting used to.
 
B

bayloon2

Cadet
Joined
Jun 1, 2011
Messages
6
Re: O/B Re-engine

Georgesalmon said:
Get a sailboat engine or a designed kicker. They have a different gear ratio that will turn a large 4 blade prop and give you the push you need. You can only get displacement speeds withot planing the hull. So you need a high torque motor. Good example would be a 9.9 merc pro-kicker, or Yamaha has an 8hp thats high torque to. 4 stroke is quieter.
Click to expand...

robert graham said:
There's several electric outboards on the market(Torqueedo, others)that might be worth consideration....Totally Quiet...plenty for 300 acre lake! Install a battery charger and you're good to go!...QUIET!;)
Click to expand...

Thnx for the quick replies. I'll check out everything industry has to offer in both high-thrust and electric O/B's. Wayne
 
R

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Re: O/B Re-engine

Home Cookin' said:
Galley slaves. And if you're good at it you can keep them right quiet.

Just that incessant drum beat takes some getting used to.
Click to expand...
My 2nd on the galley slaves!...after you get used to feedin' 'em, the drums and the potty breaks, you'll be good to go!:D:p
 
S

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: O/B Re-engine

bayloon2 said:
Here's the situation:

I am completely refitting a near basket-case 30-year old Bayliner 2850 Contessa Sunbridge (27.5' LOA express cruiser) project boat for use exclusively on a small (less than 300 acres) protected lake. The factory engine, outdrive, fuel tank, windshield, and many other broken/non-functioning items have been eliminated reducing weight to around 5,000 lbs. My intent is to mount a single tiller O/B on the swim platform for leisurely, relatively quiet cruising around the lake on calm days. Ideally, I'd like to be able to get hull speed at idle out of a 9.9HP, but we all know that's a bridge too far. Barring an emergency, I don't intend to run at WOT, so I prefer to compromise speed for quiet. A couple MPH would be just fine at low throttle.

So with this thumbnail background, I'd sure appreciate your wisdom on what direction I should go. Thnx.
Wayne
Click to expand...

Years back I had a 1977 Victoria Flybridge with a 350 ci GM engine coupled to a Volvo OD. I put a 1975 9.9 on the ob bracked just for grins as it was all I had. Was down in the keys one time when the 350 died. Got the 5 miles or so back to the marina with the 9.9. Will a 9.9 work - - yeah but only in near zero wind conditions.

Oh - and sold the sucker six weeks before hurrricane Andrew ripped through the neighborhood. It had a triple axle trailer and scared the hell out of me going down the road.
 
B

bayloon2

Cadet
Joined
Jun 1, 2011
Messages
6
Re: O/B Re-engine

Georgesalmon said:
Get a sailboat engine or a designed kicker. They have a different gear ratio that will turn a large 4 blade prop and give you the push you need. You can only get displacement speeds withot planing the hull. So you need a high torque motor. Good example would be a 9.9 merc pro-kicker, or Yamaha has an 8hp thats high torque to. 4 stroke is quieter.
Click to expand...

Assuming I go with a high-thrust 4-stroke and given I want to max out speed (up to hull speed) with minumum RPM, is there any wisdom in a 4-bladed prop and/or prop nozzle similar to Prop Guard (http://www.propguard.net/index.html)?
 
G

Georgesalmon

Lieutenant Commander
Joined
Apr 14, 2012
Messages
1,793
Re: O/B Re-engine

Most 4 stroke high thrust will already have a 4 blade. Your link won't work for me so don't know what prop guard is. My 9.9 merc pro-kicker will push my 20' very heavy hull at about 8mph gps, WOT. The high thrust does help a lot with turning and it makes little difference what the wind and waves are.
 
B

bayloon2

Cadet
Joined
Jun 1, 2011
Messages
6
Re: O/B Re-engine

Senior Chief...
Thnx for that tidbit of info about 4 blades coming on high-thrust O/Bs. Apparently the manufacturers have already done the testing and found that's the way to go. I guess I just wasn't looking close enough while perusing their websites and products. And it's certainly encouraging knowing you're getting GPS-verified 8 MPH outta your 9.9 at WOT on a heavy hull. That makes me think I might be able to get a couple MPHs on my hull not too far above idle for leisurely cruising around our small lake. BTW, try this website for Prop Guard info: www.propguard.net Don't have any independent reviews if it really works or not, but the science seems sound.
Wayne
(USAF Ret.)
 
You must log in or register to reply here.
Top